Senator Elizabeth Warren (D-MA) (C) speaks to reporters during a news conference a day after two explosions near the finish line of the Boston Marathon in Boston, Massachusetts April 16, 2013. REUTERS/Jessica Rinaldi

Senator Elizabeth Warren (D-MA) (C) speaks to reporters during a news conference a day after two explosions near the finish line of the Boston Marathon in Boston, Massachusetts April 16, 2013. REUTERS/Jessica Rinaldi

Senator Elizabeth Warren (D-MA) (C) speaks to reporters during a news conference a day after two explosions near the finish line of the Boston Marathon in Boston, Massachusetts April 16, 2013. REUTERS/Jessica Rinaldi

Senator Elizabeth Warren (D-MA) (C) speaks to reporters during a news conference a day after two explosions near the finish line of the Boston Marathon in Boston, Massachusetts April 16, 2013. REUTERS/Jessica Rinaldi

Senator Elizabeth Warren (D-MA) (C) speaks to reporters during a news conference a day after two explosions near the finish line of the Boston Marathon in Boston, Massachusetts April 16, 2013. REUTERS/Jessica Rinaldi

Senator Elizabeth Warren (D-MA) (C) speaks to reporters during a news conference a day after two explosions near the finish line of the Boston Marathon in Boston, Massachusetts April 16, 2013. REUTERS/Jessica Rinaldi

Senator Elizabeth Warren (D-MA) (C) speaks to reporters during a news conference a day after two explosions near the finish line of the Boston Marathon in Boston, Massachusetts April 16, 2013. REUTERS/Jessica Rinaldi

FILE - This Oct. 5, 2012 file photo shows Boston Mayor Tom Menino during a campaign event for Senate candidate Elizabeth Warren in Boston. Menino on Friday, Dec. 21, 2012, responded to the National Rifle Association's call for armed police and security volunteers to be posted at schools, saying the group's proposal "is not a plan, but a ploy to bring more guns into our neighborhoods," following the Dec. 14 massacre in a Connecticut elementary school. (AP Photo/Josh Reynolds, File)

FILE - In this Thursday, Nov. 8, 2012, file photo, U.S. Sen.-elect Elizabeth Warren, D-Mass., left, faces reporters as Mass. Gov. Deval Patrick, right, looks on during a news conference at the Statehouse, in Boston. Senate Majority Leader Harry Reid wants Massachusetts Sen.-elect Elizabeth Warren to join the Banking Committee. A Senate Democratic official confirmed Tuesday, Dec. 4, 2012, that Warren's appointment was likely, but cautioned nothing was final until the Democratic caucus approves the move. The official spoke on condition of anonymity because no announcement has been made.(AP Photo/Steven Senne, File)